Journal of Spatial Hydrology Spring vol. 5 no. 1 # The study reported here is the part of the research work submitted to Jawaharlal Nehru Technological University, Hyderabad, India by the senior author for the award of Ph.D. 1 Agriculture & Soils Group, National Remote Sensing Agency (Department of Space, Govt. of India), Balanagar, Hyderabad – 500 037, India (E-mail/ Kandrika: sreenivas_k@nrsa.gov.in_ A SPATIALLY DISTRIBUTED EVENT-BASED MODEL TO PREDICT SEDIMENT YIELD # Sreenivas Kandrika and Venkataratnam, L. 1 ABSTRACT A study has been conducted in three sub-watersheds to model the spatial distribution of runoff and sediment yield. The basic structure of the model includes generation of runoff using SCS curve number (CN) method and soil detachment by RUSLE, MUSS and MUST equations, which is in turn delimited by Kirkby’s transport capacity equation. The input parameter grids – cover, practice and soil erodibility grids were generated from satellite data with adequate field check. Routing of runoff and sediment was done in ARC/INFO’s GRID module. Predicted results were validated with field-measured values. Results show that the runoff from CN method was better estimated after accounting for depression storage. Results from two hilly watersheds show that the standard error of sediment yield prediction of RUSLE < MUSS < MUST equations. In a relatively flat watershed, sediment yields were underestimated, due to underestimation of transport capacity. Hence, there is a need to address the transport capacity in plains and moderately sloping areas. Keywords: Runoff, sediment yield, GIS, remote sensing, watershed, event-based. INTRODUCTION Soil erosion is a complex dynamic process by which productive soil surface soil is detached, transported and accumulated at a distant place resulting in exposure of subsurface soil and siltation in reservoirs and natural streams elsewhere. Economically, the soil loss results in the decrease of arable land and its quality by depleting the top fertile soil and affecting the land productivity. It also affects the surface water storage capacity and by sedimentation of lakes and reservoirs; and water quality by contaminating the water with suspended soil particles, toxic materials and pesticides. Though the soil erosion is said to be the natural process, it could be detained or accelerated by human intervention. Surface mining, deforestation, improper land husbandry, etc. could aggravate the problem. Soil erosion is problem per se though out the world. Globally, 1,964.4 M ha of land is affected by human-induced degradation (UNEP, 1997). Of this, 1,903 M ha are subject to soil erosion by water and 548.3 M ha by wind erosion. In India about 5334 MT of soil is eroded annually though the total river carrying capacity is 2052 MT (Narayana and Rambabu, 1983). As per the Ministry of Agriculture (1985) about 113.3 M ha of land is subjected to soil erosion by water.